Because of the ever increasing demand placed on electrical components, in general, electronic designers need to be able to pack higher powered components closer together in ever smaller spaces. More power in less space translates to higher watt densities, and therefore, increased heat generation. As temperatures rise, the reliability and functionality of electronic components are impaired dramatically. Experience has shown that more than 50 percent of electronic failures are the result of thermal problems. Traditionally, heatsinks are used to move heat from components generating the heat to an area where the heat can be dissipated to the atmosphere or adequate ventilation can be provided to the heatsink.
Conventional heatsinks use some type of mechanical method to attach the heat-generating component to the heatsink. The most common methods are: adhesives, spring clamping devices, or hold-down brackets with a mechanical fastener such as a machine screw. These methods generally require an assembler to make the mechanical attachment of the component to the heatsink.
Heat-generating electronic devices need to be electrically isolated from the heatsink in many cases. Currently the devices are electrically isolated by a thermal interface pad, which results in a substantial thermal contact resistance. Typically, in a stamped heatsink assembly, the presence of the thermal interface pad can contribute up to 50 percent of the overall thermal resistance, even in the best designs. However, heat generating devices may be directly mounted on the heatsink. In at least one conventional approach, the entire heatsink is covered with a dielectric material prior to mounting the device on an intervening metal foil layer. By covering unnecessary areas of the heatsink with the dielectric, the thermal efficiency of forced convection cooling is significantly reduced. When the device is surface mounted, the contact resistance is very low, because of the metal to metal bond between the tab of the device and the metal foil substrate.
There are additional thermal transfer inefficiencies associated with the way in which components are conventionally attached to the heatsink. Although the component surface and the mating surface appear to be smooth, under adequate magnification it can be shown that they are actually rough. When a heatsink is mated with a heat-generating device by a mechanical means such as a spring clamp or hold-down bracket, microscopic peaks in the surface of the component ride upon corresponding microscopic peaks of the heatsink. Therefore, the two surfaces are not in the close physical proximity that fosters good heat transference by conduction. Of course, this poor thermal conductivity results in higher device temperatures which, in turn, lead to device failures. Alternatively, adhesives are often used to adhere the electrical component to the heatsink; however, these conventional adhesives also bring disadvantages. For example, while these adhesives often have good dielectric characteristics, they are not good thermal conductors, or, if they are good thermal conductors, they tend to have poor dielectric characteristics. Thus, these present day adhesives do have undesirable characteristics.
Accordingly, what is needed in the art is a heatsink with a low thermal impedance between the electronic component and the body of the heatsink while maintaining good dielectric characteristics and eliminating mechanical fasteners.